The detection and quantification of biomarkers has various applications, including food and water safety, personalized medicine, and the detection of biothreat agents. In the context of medical diagnostics, detection of biomarkers directly and rapidly in body fluids can significantly decrease health care cost, and possibly improve health care delivery. Current methods have high detection limits and results typically are not available quickly. For example, in medical diagnostics, detection limits are so high that biomarkers are measurable only in an advanced stage of a disease.
Pertaining to personalized medicine, the field of diagnostic proteomics (The analysis of the expression, localizations, functions, and interactions of the proteins expressed by the genetic material of an organism.) has evolved into a powerful method for detecting diseases. The current industry standard in protein diagnostics is enzyme-linked immunosorption assay (ELISA) which has ˜pM (picomoles/liter) detection limit and relies on fluorescent labeling. Application of ELISA is limited to a point-of-care setting due to sample preparation and the reliance on maintenance-intensive equipment and skilled personnel. Emerging approaches include immuno-PCR, immunoassay in conjunction with multi-photon detection method (IA-MPD), and super-ELISA. These approaches have disadvantages, such as, requiring sample preparation steps, labeled reagents, multi-step laboratory procedures requiring skilled laboratory personnel, and handling of hazardous materials. For example, super-ELISA requires labeling with multiple copies of a color-generating enzyme and multi-photon detection utilizes radioactive Iodine.
Also pertaining to personalized medicine, prostate cancer is one of the most common forms of cancer among men in the United States and the second leading cause of death. Prostate cancer screening is evolving, with no well-accepted guidelines to date. Currently, prostate cancer is screened using annual serum prostate specific antigen (PSA) evaluation and digital rectal exam (DRE). PSA is the most common biomarker used for the diagnosis and the prediction of staging prostate cancer. PSA screening has led to earlier detection of prostate cancer, however, it is not a cancer-specific marker and, therefore has a low sensitivity and specificity which limit the accurate detection of prostatic adenocarcinoma (malignant tumor). Interpretation of the serum PSA test is made on the basis of PSA levels. Depending on the level of PSA present in serum, the specificity of the PSA test for detecting prostate cancer can be low, because patients with other conditions, such as benign prostatic hyperplasia or chronic prostatitis, also exhibit increased levels of PSA. The use of PSA as an early indicator for prostate cancer has resulted in an increased number of transrectal ultrasound-guided prostate needle biopsies that show small foci of prostatic adenocarcinoma. The diagnosis of small foci of prostatic cancer on needle biopsy is a major diagnostic challenge for surgical pathologists. Both under diagnosis of a small adenocarcinoma and over diagnosis of a benign lesion can cause unnecessary treatment and expense. Additionally, misdiagnosis of a needle biopsy can be a potential liability for pathologists.